U.S. patent application number 09/891459 was filed with the patent office on 2002-02-21 for method and apparatus for fabricating semiconductor laser device.
Invention is credited to Itoh, Yoshiyuki, Kanishi, Hiroshi, Tamaishi, Masayuki.
Application Number | 20020022289 09/891459 |
Document ID | / |
Family ID | 26594860 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022289 |
Kind Code |
A1 |
Tamaishi, Masayuki ; et
al. |
February 21, 2002 |
Method and apparatus for fabricating semiconductor laser device
Abstract
After profiles of two chips are recognized on intermediate
stages and their positions are corrected, collets are used as
electrodes and a voltage is applied to the chips on bonding stage
on which the chips are bonded onto a submount. Then, the respective
two chips are allowed to emit light, final position correction is
performed on the basis of the light-emission point data and bonding
is performed. The two chips can be bonded at narrow pitches by
tilting the collets with respect to chip surfaces. Consequently,
two laser chips can be bonded at narrow pitches on one submount in
high position accuracy.
Inventors: |
Tamaishi, Masayuki;
(Kashihara-shi, JP) ; Kanishi, Hiroshi;
(Osaka-shi, JP) ; Itoh, Yoshiyuki; (Shiki-gun,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Rd.
Arlington
VA
22201-4714
US
|
Family ID: |
26594860 |
Appl. No.: |
09/891459 |
Filed: |
June 27, 2001 |
Current U.S.
Class: |
438/48 |
Current CPC
Class: |
H01S 5/02326 20210101;
H01L 21/68 20130101; H01S 5/4031 20130101 |
Class at
Publication: |
438/48 |
International
Class: |
H01L 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2000 |
JP |
2000-194317 |
May 17, 2001 |
JP |
2001-148083 |
Claims
What is claimed is:
1. A method of fabricating a semiconductor laser device wherein two
semiconductor laser chips 12, 13 are die-bonded on one submount
116, comprising processes of placing the semiconductor laser chips
on intermediate stages 109, 110, allowing the semiconductor laser
chips on the submount 116 to emit light and measuring
light-emission point positions and transferring the semiconductor
laser chips through fixed points to prescribed positions on the
submount 116.
2. The method of fabricating a semiconductor laser device according
to claim 1, including a process of measuring light-emission point
positions and light-emission axis directions of the semiconductor
laser chips placed on the intermediate stages 109, 110.
3. The method of fabricating a semiconductor laser device according
to claim 2, including a process of correcting positions and
directions of the intermediate stages 109, 110 on the basis of the
results of measuring the light-emission point positions and
light-emission axis directions of the semiconductor laser chips
placed on the intermediate stages 109, 110.
4. The method of fabricating a semiconductor laser device according
to claim 1, including processes of sucking the two semiconductor
laser chips 12, 13 from respective wafer sheets 101, 102 or a chip
tray by using collets 105, 106, transferring the collets 105, 106
through fixed points by a fixed-point transfer movement mechanism
120 and placing the two semiconductor laser chips on the respective
intermediate stages 109, 110, correcting positions of the two
semiconductor laser chips on the respective intermediate stages,
sucking the two semiconductor laser chips again, transferring the
chips through fixed points and mounting the chips on the submount
116, energizing the two semiconductor laser chips on the submount
116 to allow the chips to emit light and measuring a distance
between the light-emission points of the two chips.
5. The method of fabricating a semiconductor laser device according
to claim 4, including a process of transferring the two
semiconductor laser chips onto the submount through fixed points
and then correcting the chip positions on the basis of the measured
distance between the light-emission points by a movement mechanism
123 for fine XY movement provided separately from the fixed-point
transfer movement mechanism.
6. The method of fabricating a semiconductor laser device according
to claim 4, including processes of allowing the two semiconductor
laser chips to emit light on the submount at the same time,
measuring a distance between light-emission points and using one
light-emission point as a reference and moving the other chip to a
prescribed position on the basis of the measurement data.
7. The method of fabricating a semiconductor laser device according
to claim 4, including a process of allowing the two semiconductor
laser chips to emit light on the submount, measuring a distance
between the light-emission points and moving both the chips to
prescribed positions by using light-emission point positions
predetermined for both the semiconductor laser chips as references
on the basis of the measurement data.
8. A two-chip bonding apparatus for die-bonding two semiconductor
laser chips 12, 13 on one submount 116, having intermediate stages
109, 110 for correcting positions and directions of the
semiconductor laser chips 12, 13, a bonding stage 115 for placing a
submount 116 on which the semiconductor laser chips are bonded,
means for allowing the two semiconductor laser chips to emit light
at the same time on the submount placed on the bonding stage, means
for measuring a distance between light-emission points of the two
semiconductor laser chips and means for transferring the two
semiconductor laser chips through fixed points to prescribed
positions on the submount.
9. The two-chip bonding apparatus according to claim 8, which has
collets for sucking the semiconductor laser chips, a fixed-point
transfer movement mechanism which is connected to collet heads of
the collets to move the collets, means for recognizing profiles of
the semiconductor laser chips on the intermediate stage, means for
recognizing light emission axes of the semiconductor laser chips on
the intermediate stages, a drive mechanism for correcting positions
and directions of the intermediate stages, means for allowing the
two semiconductor laser chips to emit light at the same time on the
submount placed on the bonding stage and means for measuring a
distance between light-emission points of the two semiconductor
laser chips, and which corrects positions of the two semiconductor
laser chips on the submount and then performs bonding.
10. The two-chip bonding apparatus according to claim 9, wherein a
piezo-electric element precision drive mechanism for fine XY
movement is separately connected to the collet heads separately
from the fixed-point transfer movement mechanism.
11. The two-chip bonding apparatus according to claim 10, wherein
the piezo-electric element precision drive mechanism is driven on
the basis of the measured light-emission point distance data.
12. The two-chip bonding apparatus according to claim 9, wherein
the collets are tilted-type collets, the two tilted-type collets
are attached as opposed to each other and the two semiconductor
laser chips can be die-bonded at the same time by using the two
tilted-type collets.
13. The two-chip bonding apparatus according to claim 9, wherein a
visual field is opened by using the opposed tilted-type collets as
the collets so that a chip bonding state and a collet suction state
can be confirmed from right above the chip bonding head.
14. The two-chip bonding apparatus according to claim 9, wherein
the collets are eccentric-type collets, the two eccentric-type
collets are attached as opposed to each other and the two
semiconductor laser chips can be die-bonded at the same time by
using the two eccentric-type collets.
15. The two-chip bonding apparatus according to claim 12, wherein a
pair of collets are provided for each of the intermediate stages
and the bonding stage.
16. The two-chip bonding apparatus according to claim 9, wherein
the collets are fabricated with a tungsten cobalt carbide (WC--Co)
superhard metal sintering material, the collets are used as chip
light-emitting electrodes and the chips are allowed to emit light
by applying a voltage to the collets.
17. A collet which is fabricated with a tungsten cobalt carbide
(WC--Co) superhard metal sintering material and can be used as a
chip light-emitting electrode to allow a chip to emit light.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an apparatus and a method
for bonding two semiconductor laser chips at narrow pitches on one
submount in high accuracy. The present invention is utilized in an
apparatus for bonding the two laser chips (for example, combination
of a red chip and an infrared chip or the like) such as a
combination laser die-bonder or the like.
[0002] One example of a conventional one-chip bonding apparatus is
explained below. Conventionally, a semiconductor laser chip 4 is
vacuum-sucked by using a vertically provided vacuum-suction collet
6, peeled from a wafer sheet 1, transferred to an intermediate
stage 2 and passed as shown in FIGS. 1 and 2. On the intermediate
stage 2, a chip profile is recognized by image processing and then,
a light-emission axis is recognized. A chip position is corrected
in X, Y and .theta. directions on the basis of this data.
[0003] After the chip position is corrected in the X, Y and .theta.
directions on the intermediate stage 2, the chip is sucked again by
using the suction collet 6 and transferred onto a submount 5 placed
on a bonding stage 3. The chip is bonded onto the submount 5 as it
is with an adhesive or by thermo-compression bonding.
[0004] That is, the chip position is corrected only on the
intermediate stage in the above-described conventional one-chip
bonding apparatus. Therefore, when the chip is passed to the
submount by using the collet after the position correction on the
intermediate stage and the chip is mounted on the submount, a fine
shift occurs. Thus, bonding position accuracy according to a
specification (.+-.2 .mu.m or less) could not be ensured, thereby
resulting in variations in a laser direction.
[0005] A method of efficiently fabricating a semiconductor laser
without variations in a light-emitting direction in a die-bonding
process of a semiconductor laser is disclosed in Japanese Patent
Laid-Open Publication No. 7-202347. In this method, a laser chip is
energized and allowed to emit light on the intermediate stage by
using a probe. A light-emission axis direction is measured by image
processing and the laser chip position is corrected on the basis of
the measured value. When the light-emission axis direction is
within a certain error range, the laser chip is sucked and
transferred by a laser chip feed mechanism for die-bonding. Thus,
the chip position accuracy is improved.
[0006] When a two-chip semiconductor laser device is fabricated,
two kinds of light-emitting chips having different wavelengths are
bonded on one submount with favorable accuracy. The chips 12, 13
are bonded one by one in FIG. 3A. When the second chip 13 is
bonded, heat is applied to the first already bonded chip 12 at its
junction and the clip 12 comes off. Therefore, the two chips need
to be bonded at the same time.
[0007] In FIG. 3B, two conventional collets are simply arranged in
a mirror image to constitute a two-chip bonding by using the
one-chip bonding apparatus in FIG. 2 so that two laser chips are
die-bonded on a submount.
[0008] Since a specification for a distance between light-emission
points is 100.+-.2 .mu.m in the two-chip semiconductor laser
device, the chips need to be bonded so that a distance between the
respective light-emission points 14, 15 of the two laser chips 12,
13 is 100.+-.2 .mu.m as shown in FIG. 4. It is shown, however,
that, since the collets are vertically disposed in a constitution
shown in FIG. 3B, the collets interfere with each other and thereby
the two chips cannot be bonded closely.
[0009] In the method disclosed in Japanese Patent Laid-open
Publication No. 7-202347 as well, it is shown that, since the
collets are vertically disposed, the collets interfere with each
other and thereby the two chips cannot be bonded closely.
[0010] To prevent the collets from interfering with each other in
the constitution where the collets are vertically disposed, a
diameter of the main body of a collet might be made thinner than
the chip profile. However, currently the diameter of the main body
of the collet cannot be made thinner than the chip profile because
a vacuum hole for vacuum-sucking a chip needs to be provided,
rigidity larger than a certain level is required due to a load
applied upon chip suction and chip bonding and the collet needs to
be shaped so that position accuracy in attachment/replacement of
the collet can be easily ensured.
[0011] As described above, when the above conventional devices are
simply arranged laterally in a mirror image when a semiconductor
laser device in which two laser chips are die-bonded on a submount
is fabricated, there are disadvantages described below.
[0012] (1) Since the position is corrected only on the intermediate
stage, a fine shift occurs after the correction on the intermediate
stage when the chip is passed by using a collet or the chip is
placed on the submount.
[0013] (2) The specification required distance (x in FIG. 4)
between the light-emission points of the two chips is as narrow as
100 .mu.m. Therefore, when the two chips are bonded at the same
time, the normal vertical collets interfere with each other and
thereby the two chips cannot be bonded at desired positions at the
same time even if the light-emission point is positioned as closely
to an end of the chip as possible.
SUMMARY OF THE INVENTION
[0014] The present invention was accomplished from the above
viewpoints. Accordingly, an object of the present invention is to
provide an apparatus and a method for bonding two semiconductor
laser chips on one submount at narrow pitches in high accuracy.
[0015] In order to achieve the above object, there is provided a
method of fabricating a semiconductor laser device wherein two
semiconductor laser chips are die-bonded on one submount,
comprising processes of placing the semiconductor laser chips on
intermediate stages, allowing the semiconductor laser chips on the
submount to emit light and measuring light-emission point positions
and transferring the semiconductor laser chips through fixed points
to prescribed positions on the submount.
[0016] That is, in the present invention, a position of each
semiconductor laser chip is corrected by profile recognition and
light-emission axis recognition on the intermediate stage, a
voltage is applied to each chip by using a collet as an electrode
on a bonding stage for bonding the chip on the submount to allow
each of the two chips to emit light, the light-emission point
position data is subjected to image processing, the position of
each of the two chips is finally corrected by a high-resolution
precision positioning mechanism driven by a piezo-electric element
of a bonding head on the basis of the data and then bonding is
performed. Thus, according to the fabricating method of the present
invention, a two-chip semiconductor laser device can be fabricated
in high bonding accuracy.
[0017] In one embodiment of the present invention, the method
comprises a process of measuring light-emission point positions and
light-emission axis directions of the semiconductor laser chips
placed on the intermediate stages.
[0018] In one embodiment of the present invention, the method
comprises a process of correcting positions and directions of the
intermediate stages on the basis of the results of measuring the
light-emission point positions and light-emission axis directions
of the semiconductor laser chips placed on the intermediate
stages.
[0019] In one embodiment of the present invention, the method
comprises processes of sucking the two semiconductor laser chips
from respective wafer sheets or a chip tray by using collets,
transferring the collets through fixed points by a fixed-point
transfer movement mechanism and placing the two semiconductor laser
chips on the respective intermediate stages, correcting positions
of the two semiconductor laser chips on the respective intermediate
stages, sucking the two semiconductor laser chips again,
transferring the chips through fixed points and mounting the chips
on the submount, energizing the two semiconductor laser chips on
the submount to allow the chips to emit light and measuring a
distance between the light-emission points of the two chips.
[0020] In one embodiment of the present invention, the method
comprises a process of transferring the two semiconductor laser
chips onto the submount through fixed points and then correcting
the chip positions on the basis of the measured distance between
the light-emission points by a movement mechanism for fine XY
movement provided separately from the fixed-point transfer movement
mechanism.
[0021] Therefore, according to the present invention, two chips are
once placed on respective intermediate stages, a profile and a
light-emission axis of each chip are recognized by a camera, the
chip position is corrected by image processing and the chip whose
position is corrected is transferred onto a submount through fixed
points from left and right. Therefore, a shift on the submount
occurs only when the chip is passed after the profile recognition.
Therefore, light-emission points of the two chips can be easily
recognized even in a narrow visual field of a high-magnification
camera.
[0022] When the chip position is not corrected on the intermediate
stage, the two chips may hit each other due to a large shift upon
pickup of the chips since the gap between the two chips is narrow.
However, this can be prevented.
[0023] Since the distance between the light-emission points of the
two chips on the submount is measured to confirm that the chips are
at prescribed positions and then thermo-compression bonding is
performed, bonding can be performed in high accuracy.
[0024] That is, according to the present invention, positions of
the two semiconductor laser chips are corrected on the intermediate
stages by image processing. Since the distance between
light-emission points of the two semiconductor laser chips is
further measured on the submount to correct the positions, bonding
can be performed with a more accurate distance between the two
chips as compared with a conventional method wherein the chip
position is corrected only on the intermediate stage.
[0025] When no problem occurs upon the above-described pickup of
the chip, the position can be roughly corrected on the intermediate
stage. Consequently, a process time can be shortened on the
intermediate stage so that the apparatus tact can be shortened.
[0026] In one embodiment of the present invention, the method
comprises processes of allowing the two semiconductor laser chips
to emit light on the submount at the same time, measuring a
distance between light-emission points and using one light-emission
point as a reference and moving the other chip to a prescribed
position on the basis of the measurement data.
[0027] According to the above embodiment, bonding can be performed
accurately and the apparatus can be constituted at a relatively low
cost, since only one chip bonding head needs to have a fine
adjustment mechanism.
[0028] In one embodiment of the present invention, the method
comprises a process of allowing the two semiconductor laser chips
to emit light on the submount, measuring a distance between the
light-emission points and moving both the chips to prescribed
positions by using light-emission point positions predetermined for
both the semiconductor laser chips as references on the basis of
the measurement data.
[0029] According to the above embodiment, bonding can be performed
accurately and, by providing both the chip bonding heads with a
fine adjustment mechanism, not only a relative position between the
two chips, but also an absolute position of each laser chip with
respect to the submount can be determined in high accuracy.
[0030] Also, there is provided a two-chip bonding apparatus for
die-bonding two semiconductor laser chips on one submount, having
intermediate stages for correcting positions and directions of the
semiconductor laser chips, a bonding stage for placing a submount
on which the semiconductor laser chips are bonded, means for
allowing the two semiconductor laser chips to emit light at the
same time on the submount placed on the bonding stage, means for
measuring a distance between light-emission points of the two
semiconductor laser chips and means for transferring the two
semiconductor laser chips through fixed points to prescribed
positions on the submount.
[0031] In one embodiment of the present invention, the apparatus
has collets for sucking the semiconductor laser chips, a
fixed-point transfer movement mechanism which is connected to
collet heads of the collets to move the collets, means for
recognizing profiles of the semiconductor laser chips on the
intermediate stage, means for recognizing light emission axes of
the semiconductor laser chips on the intermediate stages, a drive
mechanism for correcting positions and directions of the
intermediate stages, means for allowing the two semiconductor laser
chips to emit light at the same time on the submount placed on the
bonding stage and means for measuring a distance between
light-emission points of the two semiconductor laser chips, and
which corrects positions of the two semiconductor laser chips on
the submount and then performs bonding.
[0032] The conventional collets are vertically disposed as shown in
FIGS. 1 and 2. On the other hand, in the present invention, the
collets are disposed while tilted towards both the front and
lateral directions of the device as shown in FIG. 5A so that the
collets do not interfere with each other upon die-bonding of two
chips. Thus, die-bonding can be performed in favorable accuracy
with a gap between the light-emission points of 100 .mu.m.
[0033] Therefore, a tilted-type collet 16 whose end is ground so as
to be in parallel to the chip surface was developed in the present
invention so that a chip could be sucked while the collet is
tilted. FIG. 6 shows an enlarged view of the end portions of the
tilted-type collets of the present invention.
[0034] In such an eccentric-type collet 17 as shown in FIG. 5B,
die-bonding can be similarly performed in favorable accuracy with a
gap between the light-emission points of 100 .mu.m. This
eccentric-type collet 17 is obtained by soldering an eccentric
block to a conventional collet to deviate the collet end from the
center. Thus, collets are prevented from interfering with each
other.
[0035] In one embodiment of the present invention, a piezo-electric
element precision drive mechanism for fine XY movement is
separately connected to the collet heads separately from the
fixed-point transfer movement mechanism.
[0036] According to the above embodiment, in each of the bonding
heads for a red chip and an infrared chip, a precision positioning
mechanism (a piezoelectric element precision drive mechanism is
further provided on a block driven by a ball screw in the XY
direction and the collet is disposed at its ends.
[0037] In one embodiment of the present invention, the
piezo-electric element precision drive mechanism is driven on the
basis of the measured light-emission point distance data.
[0038] In one embodiment of the present invention, the collets are
tilted-type collets, the two tilted-type collets are attached as
opposed to each other and the two semiconductor laser chips can be
die-bonded at the same time by using the two tilted-type
collets.
[0039] According to the above embodiment, the two respective
semiconductor laser chips can be made close to each other while
vacuum-sucked. Thus, two-chip die-bonding with a fine gap can be
achieved.
[0040] That is, in the two-chip bonding apparatus according to the
present invention, chips are transferred through fixed points onto
the submount by using the opposed tilted-type collets 16 shown in
FIG. 5A and the chips are allowed to emit light on the submount.
Each position is corrected by using a piezo-electric element on the
basis of the light-emission point recognition data. Thus,
die-bonding can be performed by the two collets in favorable
accuracy.
[0041] In one embodiment of the present invention, a visual field
is opened by using the opposed tilted-type collets as the collets
so that a chip bonding state and a collet suction state can be
confirmed from right above the chip bonding head.
[0042] According to the above embodiment, when the collets of the
present invention are used, a bonding state can be confirmed from
right above. The positions or bonding situations of the two chips
can be monitored by disposing the camera right above the chips.
[0043] In one embodiment of the present invention, the collets are
eccentric-type collets, the two eccentric-type collets are attached
as opposed to each other and the two semiconductor laser chips can
be die-bonded at the same time by using the two eccentric-type
collets.
[0044] According to the above embodiment, the two semiconductor
laser chips can be made close to each other while vacuum-sucked.
Thus, die-bonding of two chips with a fine gap can be achieved.
[0045] That is, in two-chip bonding apparatus according to the
present invention, chips are transferred through fixed points onto
the submount by using the opposed eccentric-type collets 17 shown
in FIG. 5B and the chips are allowed to emit light on the submount.
Each position is corrected by using a piezo-electric element on the
basis of the light-emission point recognition data. Thus,
die-bonding can be performed in favorable accuracy by the two
collets.
[0046] Therefore, according to the above constitution of the
present invention, the resolution for positioning during the
fixed-point transfer may be lower than a resolution required in the
final position correction. The collets can be moved at a high speed
during the fixed-point transfer. Thus, production efficiency can be
improved.
[0047] When a position resolution is required in the final position
correction between the two light-emission points on the submount, a
high-resolution and accurate positioning can be achieved by a
piezo-electric element.
[0048] In one embodiment of the present invention, a pair of
collets are provided for each of the intermediate stages and the
bonding stage.
[0049] According to the two-chip bonding apparatus of the present
invention, since a pair of collets are provided both for the
intermediate stage and the bonding stage, position correction on
the intermediate stage and position correction on the bonding stage
can be performed at the same time. Thus, the apparatus tact can be
shortened.
[0050] To allow a chip to emit light, a probe needs to be brought
into contact with the chip surface. In a conventional device,
however, it was hard due to a small size of the chip to allow the
laser chip surface to be brought into contact with a probe while
the chip is being vacuum-sucked by a collet. However, when the
collet is made with an energizing material and the collet itself is
made with an energizing electrode, the laser chip can be energized
and allowed to emit light while vacuum-sucked.
[0051] Therefore, in the two-chip bonding apparatus of the present
invention, the collet is fabricated with an energizing material and
used as an electrode for allowing the chip to emit light. The chip
is allowed to emit light by applying a voltage to the collet.
[0052] According to the present invention, the collet is lowered
while a laser chip is vacuum-sucked and mounted on the submount.
The suction collet and the ground side on the submount can be
energized so that the chip is allowed to emit light.
[0053] In one embodiment of the present invention, the collets are
fabricated with a tungsten cobalt carbide (WC--Co) superhard metal
sintering material, the collets are used as chip light-emitting
electrodes and the chips are allowed to emit light by applying a
voltage to the collets.
[0054] According to the above embodiment, since the collet is used
as a tool for subjecting the semiconductor laser chip to
thermo-compression bonding and as an electrode, the collet needs to
have low thermal conductivity and high electric conductivity as
well as high component rigidity and high component accuracy.
Therefore, the inventors of the present invention paid attention to
a WC--Co superhard metal sintering material as a material of the
collet.
[0055] A WC--Co superhard metal sintering material has low thermal
conductivity. Since heat does not easily escape through the collet
upon thermo-compression bonding of the laser chip, this material is
effective as a material of the collet. Due to relatively favorable
electric conductivity, this material can also be used as an
electrode. Furthermore, since the WC--Co superhard metal sintering
material has high rigidity, a fine component having high accuracy
and high rigidity can be fabricated by electric discharge
machining.
[0056] Bonding in higher position accuracy could be achieved by
using the method and the apparatus of the present invention as
compared with a conventional die-bonding apparatus where chip
correction is performed by image processing only on the
intermediate stage.
[0057] That is, according to the present invention, when two
semiconductor laser chips are die-bonded on one submount, the chips
can be mounted in high accuracy with a distance between
light-emission points of the two chips within a range of 100.+-.2
.mu.m Furthermore, since final position correction is performed on
the submount, collets can be moved at high speed during fixed-point
transfer. Thus, productivity can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0059] FIG. 1 is a schematic view showing a constitution of a
conventional one-chip bonding apparatus;
[0060] FIG. 2 is a schematic view showing one example of the
conventional one-chip bonding apparatus;
[0061] FIG. 3 is schematic views showing two-chip bonding using
conventional collets,
[0062] FIG. 3A is a schematic view showing a process of bonding
chips one by one, and
[0063] FIG. 3B is a schematic view showing a process of bonding two
chips at the same time;
[0064] FIG. 4 is an explanatory view showing a bonding situation of
a submount, a red laser chip and a infrared laser chip of a
two-chip semiconductor laser device;
[0065] FIG. 5A is a schematic view showing tilted-type collets of
the present invention and
[0066] FIG. 5B is a schematic view showing eccentric-type collets
of the present invention;
[0067] FIG. 6 is an enlarged view showing ends of the tilted-type
collets of the present invention;
[0068] FIG. 7 is a schematic view showing a constitution of the
two-chip bonding apparatus of the present invention;
[0069] FIG. 8 is a schematic view showing one example of the
two-chip bonding apparatus of the present invention;
[0070] FIG. 9 is a schematic view showing one example of position
correction on an intermediate stage according to the present
invention;
[0071] FIGS. 10A-10C are schematic views showing one example of
position correction on the intermediate stage according to the
present invention;
[0072] FIGS. 11A-11D are schematic views showing one example of
position correction on the intermediate stage according to the
present invention;
[0073] FIGS. 12A-12D are schematic views showing one example of
position correction on the intermediate stage according to the
present invention;
[0074] FIG. 13 is a schematic view showing one example of position
correction on a bonding stage according to the present
invention;
[0075] FIG. 14 is a schematic view showing one example of position
correction on the bonding stage according to the present invention;
and
[0076] FIG. 15 is a view with detailed dimensions of the
eccentric-type collet of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0077] The operation procedure of bonding a red chip and an
infrared chip by using a two-chip bonding apparatus of the present
invention shown in FIGS. 7 and 8 includes the following
processes:
[0078] (1) Positions of chips to be removed from respective wafer
sheets 101, 102 for a red chip and an infrared chip are confirmed
by image processing and these chips are positioned at prescribed
positions;
[0079] (2) The chips are lifted by a lifting flash, vacuum-sucked
by collets 105, 106 and removed from the wafer sheets 101, 102;
[0080] (3) The chips removed from the wafer sheets 101, 102 are
transferred through fixed points while vacuum-sucked and then
placed on intermediate stages 109, 110;
[0081] (4) Chip shift amounts x and y from the prescribed positions
of the chips are detected by using profile recognition cameras 111,
112 and angular shift amounts .theta. are detected by
light-emission point recognition cameras 113, 114;
[0082] (5) The intermediate stages 109, 110 are moved by shift
amounts x, y, .theta. by an X, Y, .theta. drive mechanism (not
shown) so that the chip positions are corrected to the prescribed
positions;
[0083] (6) The chips whose position is corrected are vacuum-sucked
by the collets 105, 106 and transferred through fixed points from
left and right until positioned to positions above a submount 116
placed on a bonding stage 115; and
[0084] (7) The collets sucking the red chip and the infrared chip
103, 104 from left and right, respectively, are lowered so that the
chips are brought into contact with the submount 116.
[0085] The above processes (1)-(6) can be performed for a red chip
and an infrared chip at the same time or one by one. In a
conventional device, process (7) cannot be performed at the same
time. However, this process can be performed at the same time in
the present invention.
[0086] In the conventional device, bonding is performed here and
then the procedure finishes. However, the present invention further
includes the following processes:
[0087] (8) The red chip 103 and the infrared chip 104 are
temporarily placed on the submount 116 while vacuum-sucked by the
collets 105, 106;
[0088] (9) Contact probes (not shown) are brought into contact with
interconnections which are formed on the submount 116 and have
continuity with the red chip and the infrared chip and the contact
probes and the respective collets are energized to allow the two
chips to emit light;
[0089] (10) The light-emission points 117, 118 of these two chips
are recognized by one camera 119 for recognizing a distance between
the light-emission points, the distance between the light-emission
points of the two chips and tilting angles of light emission axes
of the two light-emission points are detected and compared with
prescribed positions and shift amounts from the references are
detected;
[0090] (11) If there is a shift, electricity is turned off, the
collet is raised and the collet is driven to correct the chip
position to the reference light-emission point position by applying
a voltage matching the shift amount to a piezo-electric element
provided to each of collet heads for a red chip and an infrared
chip;
[0091] (12) After the positions are corrected, the collets are
lowered again, processes (9)-(11) are repeated a prescribed number
of times and the shifts are corrected until the distance between
the light-emission points of the two chips is within the range
according to a specification;
[0092] (13) The position correction is repeated a prescribed number
of times and if specification accuracy cannot be obtained, the
bonding procedure is deemed as an error and processed as such;
[0093] (14) When the specification accuracy is obtained, the
contact probes are raised, the submount 116 is heated while both
the collets 105, 106 are lowered and the red chip and the infrared
chip 103, 104 are bonded to the submount 116 by thermo-compression
bonding;
[0094] (15) After bonding is completed, processes (9) and (10) are
performed again to confirm position accuracy; and
[0095] (16) The collets 105, 106 are raised and returned to the
start position of the fixed-point.
[0096] In the above process (11), when the position accuracy of the
submount 116 and the two chips is not so important, one laser chip
position can be used as a reference to correct only the position of
the other laser chip. That is, highly accurate correction can be
achieved by providing a piezo-electric element adjustment mechanism
123, 124 only to the bonding head of the chip whose position is
corrected.
[0097] In the process (12), the distance between the light-emission
points of the two chips can be determined arbitrarily according to
a specification of the semiconductor laser device or the like. The
number of times of repetition can also be arbitrarily
determined.
[0098] Normally, vacuum-suction by the collet is continued during
bonding. However, vacuum-suction by the collet can be stopped and
the collet can be raised in the middle of heating in the above
process (14) so that the heat transmitted to the chip does not
escape.
[0099] Furthermore, process (16) can be omitted.
[0100] Furthermore, position correction on the intermediate stage
and position correction on the bonding stage can be performed at
the same time by providing a pair of collets both for an
intermediate stage and a bonding stage. Thus, the apparatus tact
can be shortened.
EXAMPLES
[0101] FIG. 7 shows a block diagram of the two-chip bonding
apparatus of the present invention. FIG. 8 shows one embodiment of
the invention. Examples of the present invention are explained with
reference to these drawings, but the present invention is not
limited to the following examples.
Example 1
[0102] Two-chip bonding processes for fabricating a two-chip
semiconductor laser device having a specification distance between
the light-emission points of 100 .mu.m by using tilted-type collets
according to the present invention are described below.
[0103] A. Position Correction on Intermediate Stage
[0104] First, a red chip 103 and an infrared chip 104 were removed
from a wafer sheet 101 and 102, respectively, by usual pickup
processing using a conventional technique as shown in FIG. 7 and
placed on respective intermediate stages 109, 110.
[0105] Subsequently, chip shift amounts x and y from the chip
reference position were detected by a profile recognition camera
111, 112. Also, an angular shift amount .theta. of each
light-emission axis from the reference direction was detected by a
light-emission point recognition camera 113, 114. The intermediate
stage 109, 110 was moved by the shift amounts x, y, .theta. on the
basis of the detection data to correct the chip position to the
reference position (FIG. 9).
[0106] Here, the direction of the light-emission axis of a laser
emitted from the chip is assumed as a Y direction. The vertical
direction of the chip is assumed as a Z direction. The direction
perpendicular to the YZ plane is assumed as an X direction.
[0107] Processes of correcting shifts of the chip position and
angle by profile recognition and light-emission axis recognition on
the intermediate stage are explained in detail below by using a red
chip as an example (FIGS. 10-12).
[0108] I. Correction of Shift by Chip Profile Recognition
[0109] First, chip profile is recognized by using a CCD camera
(profile recognition camera 111) capable of recognizing a chip
profile from above (FIG. 10A). To make the resolution of the
profile recognition camera 111 as high as possible, the
magnification is adjusted so that only the vicinity of a laser
outgoing end surface of the chip can be enlarged and observed (FIG.
10B). The position of an outgoing surface 128 and both side
portions 129 of the chip are detected in the profile (FIG. 10C) and
shift amounts x and y from the reference position and angular shift
amount .theta. from the reference direction are calculated. The
calculated shift amounts from the reference converted to motor
movement amounts. The intermediate stage is moved to the reference
position and the reference direction to correct the laser chip
position in the X, Y and .THETA. directions.
[0110] II. Correction of Angle by Laser Light-emission Axis
Recognition
[0111] The laser outgoing direction 130 may be tilted with respect
to the reference direction only with shift correction by profile
recognition of the chip shape as shown in FIG. 10. Therefore,
angular correction by light-emission axis recognition was further
performed.
[0112] First, the chip light-emission point position was detected
by using a CCD camera (light-emission point recognition camera 113)
capable of observing the laser light-emission point 117 from the
laser outgoing surface side and a horizontal position (x.sub.1,
z.sub.1) on the outgoing surface was determined while the outgoing
surface was focused (FIG. 11A). At this time, the origin of the XZ
plane is not limited, but was set at the center of the screen
here.
[0113] This light-emission point recognition camera 113 can be
driven in the Y direction to detect a focused light-emitting
position (FIG. 9). Therefore, while the camera was driven by steps
in the Y direction, the laser light-emission point was observed and
the beam diameter was measured by changing the y value (FIGS. 11B
and 11C). Since the beam on the laser outgoing surface is spread
laterally along an active layer of the laser chip, the beam shape
is long sideways. Therefore, in the present invention, the beam
width in a direction perpendicular to the active layer, that is,
the Z direction was assumed as a "beam diameter".
[0114] Subsequently, on the basis of the measured value obtained as
described above, the relationship of the y value and the beam
diameter was approximated by the quadratic function by using the
least square method. A y value giving the smallest beam diameter in
this approximate equation was assumed as y.sub.1 (FIG. 11C).
[0115] While the light-emission point camera from the detected
y.sub.1 was further driven in the Y direction by .DELTA.y, the
light emitting level was controlled up to the level where the light
emitting level was not saturated. The laser light-emission point
was observed and the horizontal position x.sub.2 on the outgoing
surface was detected. A tilting angle .theta. of the light-emission
axis was calculated by using the following equation (1) (FIG. 11D).
1 = tan - 1 ( X2 - X1 y ) ( 1 )
[0116] Correction amounts were calculated from the relationship of
the reference position and detected positions and the intermediate
stage 109 was moved in the X, Y and .THETA. directions.
[0117] FIGS. 12A-12D show a state after recognition and correction
of the light-emission points when this procedure was repeated and a
prescribed convergent value was obtained. Shifts of the infrared
chip were also corrected similarly.
[0118] The red chip and the infrared chip whose position and angle
were corrected were vacuum-sucked by the collets 105, 106 and
transferred through fixed points onto the submount 116 placed on a
bonding stage from left and right, respectively.
[0119] B. Final Position Correction on Bonding Stage
[0120] Position correction on the bonding stage is explained in
detail below. Methods for performing this correction include
absolute position correction, where both the chips are moved to
absolute positions with respect to the submount, and relative
position correction, where the light-emission point of one chip is
used as a reference and only the other chip is moved. In this
example, the absolute position correction was performed.
[0121] While the red chip and the infrared chip transferred through
fixed points to the bonding stage were vacuum-sucked, the collets
105, 106 were lowered. The red chip and the infrared chip 103, 104
were temporarily placed on the submount 116. Then, the respective
collets 105, 106 and the ground on the submount 116 were energized
and the two semiconductor laser chips 103, 104 were allowed to emit
light.
[0122] The light-emission points 117, 118 of the two semiconductor
laser chips were recognized by a light-emission point CCD camera
(camera 119 recognizing a distance between the light-emission
points) capable of observing the points from the side of one laser
outgoing surface.
[0123] A difference in the Z-direction position recognition due to
a difference in the wavelength of each chip was eliminated by using
a lens 131 without chromatic aberration as an optical system of
this light-emission point CCD camera. The camera 119 recognizing a
distance between the light-emission points is constituted so as to
be driven in the Y direction to detect a focused light-emitting
position (FIG. 13).
[0124] The distance between the two light-emission points and the
tilting angles of the light-emission axes of the two semiconductor
laser chips detected by the camera 119 recognizing a distance
between the light-emission points were compared with the reference
values and the shift amounts from the reference values were
measured. The positions of the two chips were corrected on the
basis of the results. FIG. 14 shows a state before and after the
position correction by recognition of the distance between the
light-emission points.
[0125] First, the laser light-emission points 117, 118 were
observed by the camera 119 recognizing a distance between the
light-emission points. The horizontal positions (x.sub.3, z.sub.3)
and (x.sub.4, z.sub.4) with respect to the outgoing surface were
detected and the distance L' between the two points were calculated
by using the following equation (2).
L'={square root}{square root over ((X4-X3).sup.2+(Z3-Z4).sup.2)}
(2)
[0126] Subsequently, while the camera 119 recognizing a distance
between light-emission points was driven by steps in the Y
direction, the laser light-emission points 117, 118 were observed
and the beam diameter was measured by changing the y value (FIG.
14). Subsequently, on the basis the measured value obtained as
described above, the relationship between the y value and the beam
diameter was approximated by a quadratic function by using the
least square method. The y values giving the smallest beam diameter
for the red chip and the infrared chip were assumed as y.sub.3 and
y.sub.4, respectively.
[0127] Each of the chips was moved in the X and Y directions by a
bonding head with a piezo-electric element which can be driven
along two axes of the X and Y directions from the two detected
light-emission points and the positions were repeatedly corrected
until the distance L' between the two points became the reference
value L (100.+-.2 .mu.m). Or, correction can be performed so that X
matches the reference value.
[0128] This procedure was repeated until the prescribed convergent
value was obtained and the positions of both the two chips were
precisely corrected by a high resolution.
[0129] In this example, the positions of both the red chip and the
infrared chip were corrected, but, for example, relative position
correction, where the red chip is used as a reference and only the
infrared chip is corrected, can be performed.
[0130] Then, the collets were raised, shifts were corrected by
applying a voltage corresponding to the shift amount to the
piezo-electric elements provided to the respective bonding heads
for the red chip and the infrared chip and the chips were moved to
the respective reference light-emission point positions.
[0131] When shifts were detected again, it was confirmed that the
positions were within prescribed accuracy. Then, bonding was
performed.
[0132] A two-chip semiconductor laser device having the distance
between the light-emission points of 100.+-.2 .mu.m in accuracy was
obtained.
Example 2
[0133] A procedure similar to Example 1 except for using
eccentric-type collets 17 of the present invention as the collets
was taken to fabricate a two-chip semiconductor laser device.
[0134] A two-chip semiconductor laser device having the distance
between the light-emission points of 100.+-.2 .mu.m in accuracy was
obtained.
[0135] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *